1. Field of the Invention
Devices for propelling through and exploring luminal cavities are disclosed. One such device example is an endoscope, which can be used to explore body passages. Such passages typically include, but are not limited to, the GI tract, the pulmonary and gynecological systems, urological tracts, and the coronary vasculature. Methods for use include exploration of the upper GI tract, including the small intestine and exploration of the lower part of the GI tract, for example the large intestine or colon.
2. Description of the Related Art
Colonoscopy is a diagnostic and sometimes therapeutic procedure used in the prevention, diagnosis and treatment of colon cancer, among other pathologies. With colonoscopy, polyps can be harvested before they metastasize and spread. With regular colonoscopies, the incidence of colon cancer can be substantially reduced.
The anus can provide entry into the colon for a colonoscopy. The colon extends from the rectum to the cecum and has sigmoid, descending, transverse, and ascending portions. The sigmoid colon is the s-shaped portion of the colon between the descending colon and the rectum.
Colonoscopy typically involves the anal insertion of a semi-flexible shaft. To typically navigate the colon, the forward few inches of tip are flexed or steered as the shaft is alternately pushed, pulled, and twisted in a highly skill-based attempt to advance to the end of the colon: the cecum. The medical professional imparts these motions in close proximity to the anus, where the device enters. Tip flexure has typically been accomplished by rotating wheels—one that controls cables that move the tip right-left, and one that controls cables that move the tip up-down.
Colonoscopes typically utilize various conduits or channels. The conduits or channels often contain elements that enable vision (e.g., fiber optics, CCD cameras, CMOS camera chips) and lighting (e.g., fiber optic light sources, high power LEDs (Light Emitting Diodes)), such as energy delivery and/or receipt conduits. They have conduits that provide suction or pressurization, fluid irrigation, the delivery of instruments (e.g., for cutting, coagulation, polyp removal, tissue sampling) and lens cleaning elements (typically a right angle orifice that exits near the camera, such that a fluid flush provides a cleansing wash).
Colonoscopes include articulating sections at their tip, which allow the user to position the tip. These articulating sections have rigid link bodies that rotate relative to each other through the use of pins at their connecting joints. As tensile cables pull from the periphery of the articulating sections, they impart torques, which rotate the link sections on their pins, articulating the tip section. The links are usually rotated by two or four tensile cables.
Typical commercially available colonoscopes are currently reusable. However, as disposable and other lower-cost colonoscopes are developed, these articulatable sections are no longer practical. Their high part count creates total costs that are exorbitant for a lower cost, disposable device. The pivot pins can also fall out, which can create a patient danger. Their design geometries, while suited for long life, high cost, high strength metals elements, do not readily suit themselves to the design goals of lower-cost and more readily mass-produced parts.
Suction can be utilized to remove debris or fluid. The colon can be pressurized to expand the diameter of the colon to enhance visualization.
During advancement of the colonoscope through the colon, landmarks are noted and an attempt is made to visualize a significant portion of the colon's inside wall. Therapeutic actions can occur at any time, but are typically performed during withdrawal.
Navigating the long, small diameter colonoscope shaft in compression through the colon—a circuitous route with highly irregular anatomy—can be very difficult. Studies have shown a learning curve for doctors performing colonoscopies of greater than two-hundred cases. Even with the achievement of such a practice milestone, the cecum is often not reached, thereby denying the patient the potential for a full diagnosis.
During colonoscopy, significant patient pain can result. This is typically not the result of colon wall contact or of anal entry. The primary cause of pain is thought to be stretching and gross distortion of the mesocolon (the mesentery that attaches the colon to other internal organs). This is commonly referred to as ‘looping’ and is a result of trying to push a long, small diameter shaft in compression as the clinician attempts to navigate a torturous colon. While attempting to advance the tip by pushing on the scope, often all that occurs is that intermediate locations are significantly stretched and grossly distorted. Due to this pain, various forms of anesthesia are typically given to the patient. Anesthesia delivery results in the direct cost of the anesthesia, the cost to professionally administer the anesthesia, the costs associated with the capital equipment and its facility layouts, and the costs associated with longer procedure time (e.g., preparation, aesthesia administration, post-procedure monitoring, and the need to have someone else drive the patient home). It has been estimated that forty percent of the cost of a colonoscopy can be attributed to the procedure's need for anesthesia.
Cleaning of colonoscopes is also an issue. Cleaning is time consuming, and lack of proper cleaning can result in disease transmission. Cleaning can utilize noxious chemicals and requires back-up scopes (some in use while others being cleaned). Cleaning also creates significant wear-and-tear of the device, which can lead to the need for more servicing.
In recent years there have been advancements in the navigation of the small intestine. One notable method is known as Double Balloon Enteroscopy. Double-balloon enteroscopy, also known as push-and-pull enteroscopy is an endoscopic technique for visualization of the small bowel. It allows for the entire gastrointestinal tract to be visualized in real time. The technique involves the use of a balloon at the end of a special enteroscope camera and an overtube, which is a tube that fits over the endoscope, and which is also fitted with a balloon. The procedure is usually done under general anesthesia, but may be done with the use of conscious sedation. The enteroscope and overtube are inserted through the mouth and passed in conventional fashion (that is, as with gastroscopy) into the small bowel. Following this, the endoscope is advanced a small distance in front of the overtube and the balloon at the end is inflated. Using the assistance of friction at the interface of the enteroscope and intestinal wall, the small bowel is accordioned back to the overtube. The overtube balloon is then deployed, and the enteroscope balloon is deflated. The process is then continued until the entire small bowel is visualized. The double-balloon enteroscope can also be passed in retrograde fashion, through the colon and into the ileum to visualize the end of the small bowel.
Though the procedure has played a vital role in the diagnosis and treatment of disease in this part of the GI tract, it remains problematic in several regards. Like colonoscopy, it suffers from looping. A long and flexible shaft is pushed, but instead of the tip moving forward, it often merely moves inadvertently in intermediate locations. The procedure requires significant skill, is laborious and time consuming—usually taking more than an hour.
In both colonoscopy and in navigation of the small intestine, it would be advantageous to have a device that enabled local ‘pull’ motion, i.e., if the device could pull itself forward locally, rather than having to be pushed at a far proximal and less effective location.
Methods have been suggested which create a force reaction location outside of the body. Others have been suggested which create a force reaction location—necessary to advance the endoscope—within the body, including local to the endoscope tip. Internal devices typically operate proximal to the tip's articulating section, which can be kinematically disadvantageous relative to being located distal to the articulating section.
Endoscopic devices have found it notably challenging to create methods to appropriately navigate through torturous geometries, particularly without undue colon wall stresses and subsequent mesocolon stretch. Steering kinematics are critical and have been an ongoing challenge—certainly for existing colonoscopes (which result in ‘looping’), but also to more effective next-generation devices.
The systems proposed to-date have geometries that create suboptimal steering efficacies. When a propulsion element is substantially distal to the tip articulating section, it can be vectored in that direction when propelled. This can be highly advantageous relative to systems in which the propulsive element is located proximal to the articulating section. In this situation, disadvantageous kinematics are created when the tip is retroflexed and is pointing in one desired direction of advance and the system advance is attempted. The system does not move in the direction of the retroflexed tip, but rather in the direction of the system proximal to that section. When the system is coaxial, these directions are the same. However, should the tip be retroflexed back 180 degrees, the desired advance direction (i.e., tip pointing direction) and actual advance direction are 180 degrees apart. The driven section presumes a vector—typically an axial manner—with the steering tip only having efficacy as it relates to its interaction with luminal walls. In endoscopy, this wall interaction is undesirable—it creates unnecessary wall stress and trauma, and can be a significant contributor to gross wall distortion, known as looping. It would therefore be desirable to have system designs that enable more lumen-centric steering that can point the articulating section in a direction and move in that pointed direction as the unit is advanced through the colon's straights and curvatures.
Such kinematic enablement could be achieved through a novel, dedicated system. Alternatively, it could be enabled through a device that worked additive to existing endoscopes. This would be advantageous, in that it would utilize a vast installed base of advanced hardware, software, and training. Such ‘retrofit’ devices could potentially achieve scaled utilization in an accelerated manner.
Devices to achieve these performance goals will often have challenges with optimal material selection. The desired structure can have a rare combination of requisite features: softness, strength, radial stiffness, low thickness, freedom from leaks, flex-crack resistance, puncture resistance, appropriate coefficient of friction, the potential for modifiable geometry as a function of length, and appropriate manufacturability and cost. Monolithic materials often prove insufficient at providing the variety of requisite specifications.